1. Field of Art
This invention generally relates to optical touch-sensitive devices, especially an augmented optical waveguide for use in an optical touch-sensitive device.
2. Description of the Related Art
Touch-sensitive displays for interacting with computing devices are becoming more common. A number of different technologies exist for implementing touch-sensitive displays and other touch-sensitive devices. Examples of these techniques include, for example, resistive touch screens, surface acoustic wave touch screens, capacitive touch screens and certain types of optical touch screens.
However, many of these approaches currently suffer from drawbacks. For example, some technologies may function well for small sized displays, as used in many modern mobile phones, but do not scale well to larger screen sizes as in displays used with laptop or even desktop computers. Another drawback for some technologies is their inability or difficulty in handling multitouch events. A multitouch event occurs when multiple touch events occur simultaneously. Another drawback is that technologies may not be able to meet increasing resolution demands.
Another drawback for some optical touch-sensitive devices is that light propagation in optical waveguides in such devices may be altered by attaching materials (e.g., a display) with unknown optical properties to the optical waveguides. Light typically propagates in such an optical waveguide via total internal reflection (TIR). TIR usually requires light to be trapped in a transmission medium that has a higher refractive index than its surrounding materials (usually air, with a refractive index of approximately 1). Any object with unknown optical properties, or optical properties incompatible with TIR, that is in contact with the optical waveguide will likely reduce the optical energy propagating in the waveguide. This may make measurement of touch-induced transmission loss more difficult and lower touch sensing robustness, adversely affecting the touch sensing performance of such an optical touch-sensitive device.
Thus, there is a need for augmented optical waveguides for use in optical touch-sensitive systems.